1. Field of the Invention
The present invention relates to a modular structural composite beam. In particular, the present invention relates to a modular structural composite beam for use in a wind turbine blade.
2. Description of the Related Art
Large wind turbine blades (>35 m in length) are typically constructed by forming a strengthening and stiffening cantilever beam or box spar inside an aerodynamic fairing. The current approach to manufacturing wind turbine blades is to produce each blade either as two half shells with a separate beam, or as two half shells with an integral beam. In both cases, the two half shells are bonded together along their edges to form the complete blade.
The structural beam comprises flanges at either end which are connected to one another by one, or more commonly two, shear webs. The flanges are made from predominantly unidirectional fibre reinforced plastic and the shear webs consist of predominantly multi-axial (+/−45°) fibre reinforced plastic.
It is well known in the art to make the beam by moulding the flanges within the half shells of the aerodynamic fairing and then bonding the flanges together with the shear webs when the aerodynamic fairings are joined together. Alternatively the beam is made by moulding a separate beam on a separate tool and then bonding the beam into the aerodynamic fairings when they are joined together.
These methods each have a number of shortcomings. Firstly, if the unidirectional flange of the beam is moulded within the fairing it is difficult to accurately control the quality of the flange material. This typically results in poor mechanical properties from the flange material leading, in turn, to increased mass required for engineering safety and therefore increased cost.
If the beam is made separately by moulding on a separate tool some of the above shortcomings may be avoided. However, the cost of the separate tool adds to the overall cost of the component.
In either case, if a new design or a slight variation in design is required, completely new tools need to be made thereby increasing prototyping time and cost also increasing the cost introducing new models. Similarly, if the use of automation is considered, the cost of automation will be high since then it must be capable of dealing with a number of different beam designs and geometries.